A system and a holder, in particular a lighting device, of the above type are disclosed by U.S.-A-5352957.
The prior art system comprises a number of appliances, such as motors and lighting devices of several types, e.g. gas discharge lamp, halogen radiator, arc lamp or normal incandescent lamp. Each appliance has associated therewith an individual local control unit comprising a bus controller, a memory and a control switch connected to a 220 V mains supply and through a bus to a central command generator, called central control unit hereinafter.
Before its physical installation the appliances to be mounted therein each contain an original address formed by a production number which is specific for a receiver of the appliance. Therefore, originally all local control units have different original addresses. After physical installation of the system it is tested. Subsequently the central control unit transmits a single command to all local control units to poll their original addresses. When receiving a proper original address in return an operational address is selected based on a predetermined plan and the central control unit will transmit a message containing a command for the local control unit with said original address to store the selected operational address in the memory of the local control unit. A local control unit continues to transmit its original address until it receives a specific message from the central control unit in return. Following the transmission of the polling command by the central control unit of the prior art system it is likely that collision of returned messages from different local control units occur. This might even lead to endlessly repeating transmission of such return messages by local control units. In that case the step of allocating operational addresses to the appliances of the system may not come to an end, by which the system cannot be brought into operation.
With the prior art system it is necessary to make a note of the different original addresses of the mounted appliances associated with their specific locations in order to be able to use said predetermined plan to allocate specific operational addresses to specific ones of the appliances, so that they can be controlled each individually on demand during proper operation of the system.
Therefore the steps of the physical installation of the system, making notes of the original addresses of its appliances inclusive, and allocating operational addresses to the appliances with the prior art system are time consuming and therefore expensive.
The invention relates, in particular, to a display system for use in appliances having a large number of light emitters, such as gambling machines and illuminated news trailers.
A display system of the above mentioned type is known in practice for use in gambling machines in which the light emitters are incandescent lamps.
According to a first known possibility for the connection of the light emitters to the central control unit, first connections of the light emitters are connected to a common supply conductor and second connections of the light emitters are connected to another supply conductor via an individual switching means. Although the central control unit is simple in this case, the large number of connecting points, the extensive wiring and the difficulty in being able to change the wiring are great drawbacks.
According to another known possibility for connecting light emitters to the central control unit, each light emitter is connected in series with a diode and each series connection of a light emitter and a diode is connected in the same polarization direction between a row and a column of a matrix and the rows and columns are connected to two supply conductors via individual switching means. Although the number of connecting points is in this case limited, the selective control of the rows and columns makes the central control unit complicated. Furthermore, in the case of use in gambling machines and illuminated news trailers, for example, extensive wiring is nevertheless necessary and this, like the matrix, is difficult to change. Another drawback is that the light emitters can be activated simultaneously only in a limited number of combinations without other light emitters also being unintentionally activated. As a result, in designing the system, account has to be taken of the light output of the various light emitters or groups of light emitters and of the individual activation or time-dependent activation per group of the light emitters. This makes the design troublesome and expensive and presents a drawback to changing the design.
In display systems of the above mentioned type, it is known to make use of a holders for light emitters which have blade contacts into which conductors for connection to the central control unit can be pressed, as a result of which the necessary electrical contacts can be effected without other means and operations. The above mentioned drawbacks, however, continue to apply.